Surfactant kinetics in newborn infants with pneumonia and Respiratory Distress Syndrome

The role of pulmonary surfactant in neonatal pneumonia is largely unknown and treatment with exogenous surfactant remains controversial. Objective. To measure (a) the amount of disaturated phosphatidylcholine surfactant recovered from tracheal aspirates and (b) its half-life in 4 groups of newborns: full-terms with pneumonia, preterms with pneumonia, full-terms with normal lung, and preterms with Respiratory Distress Syndrome. Methods. All infants received an intratracheal tracer dose of 13C labeled disaturated phosphatidylcholine. In full-terms with pneumonia, preterms with pneumonia, and preterms with Respiratory Distress Syndrome tracer was added to exogenous surfactant. Amount of desaturated-phosphatidylcholine and isotopic enrichments were measured from serial tracheal aspirates by gas chromatography and gas chromatography-mass spectrometry. Results. The amount of desaturated-phosphatidylcholine was not different in the four study groups whereas its half-life was significantly shorter in full-terms with pneumonia (19.3 ± 7.3 h), preterms with pneumonia (34.8 ± 9.4 h), and preterms with Respiratory Distress Syndrome (28.7 ± 15.9 h) compared to full-terms with normal lung (61.8 ± 28.6 h), p = 0.002. By multiple regression analysis the cumulative dose of exogenous surfactant and the oxygenation index were significant predictors of disaturated phosphatidylcholine half-life (R2 = 0.5 p = 0.03). Conclusion. Term and preterm newborns with pneumonia and Respiratory Distress Syndrome exhibited much shorter desaturated-phosphatidylcholine half-lives than term newborns with normal lungs. Larger amounts of exogenous surfactant were associated in our study with a less severe shortening of disaturated phosphatidylcholine half-life.